JPS62286805A - Pneumatic tyre for heavy load - Google Patents

Abstract

PURPOSE:To improve the resistivity against uneven wear, chipping and moisture of the entitled tyre which has a tread pattern including blocks by forming a closed sipe at each of the blocks. CONSTITUTION:Internal and external double closed sipe 4 and 5 are formed by valcanization, laser shaping and so forth on each of a train of blocks 3 which are placed at the middle part and the opposed parts of a typer in the direction of the width thereof, whereby defining small blocks 6 and 7 having demanded surface area on the internal side of the blocks and defining other small blocks 8 on the external side of the closed sipe 5 by the sipe 5. One closed sipe 10 is formed in each of the blocks 9 in the other block row, whereby dividing the block 9 into internal and external small blocks 11 and 12. By such constitution, the resistivity against wear, chipping and moisture may be improved.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention provides a heavy-duty pneumatic tire having a tread pattern including blocks, in particular, maintaining wet resistance and wear resistance. The present invention also relates to a pneumatic radial tire that provides sufficient improvement in uneven wear resistance and chipping resistance.

(Conventional technology) One of the main functions of tires is wet resistance, or in other words, traction performance on wet roads.In addition to ensuring this performance, consideration must also be given to the design of the tire. A large number of various tread patterns have been proposed in the past.

FIGS. 4(a) and 4(b) show examples thereof, and the tires shown here both have block-type tread patterns. Also, FIG. 5(a).

(b) improves wet resistance by forming a plurality of linear sipes S completely across each block B in the tread pattern shown in FIGS. 4(a) and (b). In addition to further improvement, it also brings about an improvement in wear resistance.

(Problems to be Solved by the Invention) By the way, as shown in FIG. 5, for the purpose of improving wet resistance and abrasion resistance, each block B is formed into small blocks B by linear sipes S.

In the case of dividing the small blocks B into Since the kick-out side part K receives a larger amount of friction, uneven wear called heel-and-toe occurs, and a fifth The height is shown in figure (C)! There is a problem that a large level difference as shown in Figure 1 is generated, and here, since each small block B divided by a straight sipe S has a different shape and volume, the rigidity of each of them is different. There was a problem in that the amount of wear of each small block B3 was also uneven.

Moreover, with a tire having a tread pattern as shown in Figure 5, a phenomenon called chipping, in which the small blocks B come off, is extremely likely to occur when the vehicle suddenly starts, brakes suddenly, or when a chain is attached to the tire. There was another problem.

This invention takes advantage of the problems of the prior art and solves the problems of the prior art, and provides a heavy-load bearing that can achieve both uneven wear resistance and chipping resistance, which are in a trade-off relationship, and wet resistance and abrasion resistance. The company provides pneumatic tires.

(Means for Solving the Problems) The present invention provides a heavy-duty pneumatic tire, particularly a pneumatic radial tire, having a tread pattern including blocks, in which the blocks are provided with closed sipes.

Here, closed sipe refers to a type of sipe that surrounds a small block divided within a professional area, and includes sipes consisting only of straight grooves, sipes consisting only of curved grooves, and sipes consisting of both. shall also include, and furthermore,
This also includes cases where there are slight discontinuous portions of straight grooves or curved grooves.

(Function) According to this tire, it is possible to fully utilize the unique functions provided by the sipes, that is, wet resistance and abrasion resistance, and in particular, by making the sipes a closed sipe, multiple sipes can be used. Compared to the case where straight sipes are provided, the amount of deformation of the kick-out side portion of each small block in the direction opposite to the rotational direction of the tire is sufficiently reduced to reduce wear caused by heel-and-toe. It can be made extremely small.

That is, as shown in FIG. 5, in each small block B defined by a sipe S that has an angle close to 90° with respect to the tire equator line and completely crosses block B, the rotation of the tire The rigidity of the small block B against the force in the direction and the opposite direction becomes lower, and the small block B,
On the kick side part of the tire, the deformation cannot be effectively restrained in the opposite direction to the rotational direction of the tire. Since the deformation of the protruding side portion is effectively prevented, the friction of the protruding side portion due to the road surface and thus the amount of uneven wear can be made sufficiently small.

Further, according to the closed sipe here, since the rigidity of each small block can be easily made almost equal, there is no fear that the wear 1 of each small block will be uneven.

In addition, closed sipes are completed so that there are no free ends of the sipes, and the narrow grooves that form them do not open on the side surfaces of the blocks, so that each small block divided by the closed sipes is properly Since the sipes have such rigidity and high tear strength that the opening of the sipes is restricted, it is possible to sufficiently prevent the occurrence of chipping there.

Note that the above effect can be expected even if some discontinuity is provided in the narrow groove portion extending mainly in the circumferential direction.

(Example) The present invention will be explained below based on illustrated examples.

FIG. 1 is a trend pattern diagram showing an embodiment of the present invention, which shows a main groove 1 extending in the equatorial direction of the tire.
In a block type tread pattern in which five block rows are formed by the lateral grooves 2 extending in the direction intersecting the main grooves 1, each of the block rows located at the center and both ends in the width direction of the tire. Block 3
By forming double inner and outer closed sipes 4 and 5 using a vulcanization mold, laser processing, siping machine, etc., a small block 6 having the required surface area inside them is formed.
．． 7, and also partition other small blocks 8 on the outside by the outer closed sipe 5, and by forming a - closed sipe 10 in each block 9 of the pond block row, The block 9 is divided into two small blocks 11 and 12, inside and outside.

In this example, the inner closed sipes 4 formed on the blocks 3 of the block rows at both ends are square, and the outer closed sipes 5 are pentagonal.
The inner closed sipe 4 formed on the block 3 of the central block row has a pentagonal shape, and the outer closed sipe 5 has a hexagonal shape. can be changed as appropriate in relation to the surface area of the small block to be partitioned and other factors.

In such a tread pattern, the width of each closed sipe 4.5.10 is between 0.3 mm and 3.5 mm.
Omm is preferable. This means that when each closed sipe is formed by a blade provided in a tire vulcanization mold, if the blade thickness is less than 0.3 mm, the required blade strength cannot be achieved. On the other hand, if the sipe width exceeds 3.0+a+a, the two side walls of the sipe may come into contact with each other when the small block is deformed, and the sipe cannot function effectively. ,
This is because uneven wear and chipping are extremely likely to occur.

Figure 2 (a) is a graph showing the relationship between the sipe width and the amount of uneven wear due to heel and toe, using a tire with a sipe width of 0.3 mm as an index of 100. The quantity becomes large.

According to this graph, it can be seen that the amount of uneven wear can be kept sufficiently low within the range where the sipe side walls can come into contact with each other when the block is in contact with the ground, in other words, within the range up to 3.0+am.

Also here, each closed sipe 4°5.10
The depth is preferably 174 or more of the leading depth. That is, if the leading depth is less than 174 mm, the rigidity of the small block cannot be sufficiently reduced, and sufficient wet resistance and abrasion resistance cannot be ensured.

FIG. 2(b) is a graph showing the relationship between sipe depth and wet resistance, with the braking distance of a tire without sipes as an index of 100, where the smaller the index, the longer the braking distance. In this graph, an improvement in wet resistance is observed when the sipe depth is within the range of 174 to 1 times the leading depth. Here, the sipe depth is
If it exceeds 1, the rigidity of the block is significantly reduced, wear resistance and wet resistance are reduced, and chipping of the block is also likely to occur. Furthermore, as the sipe depth increases, the degree of damage to the belt reinforcing the tread due to biting of pebbles increases.

And further here each closed sipe 4
, 5.10, the total length in the tire width direction of each block 3.9 is 1 to 8 times the maximum length of each block 3.9 in the tire width direction, thereby ensuring sufficient wet resistance. We will ensure further improvement. That is, if the total length is less than 1 time, the rigidity of the small block will be too high, and if it exceeds 8 times, the rigidity will be too low and the wet resistance will decrease. FIG. 2(c) is a graph showing this, and shows the braking distance of a tire without sipes as an index lOO.

FIG. 3 is a tread pattern diagram showing another embodiment of the present invention. Here, this is also a block type trend pattern, and each block 13 of the block rows located at both ends in the width direction of the tire is By forming two polygonal closed sipes 14.15 adjacent to each other in the circumferential direction of the tire and sharing one side, small blocks 16.17 and 18 are respectively partitioned on the inner and outer sides thereof, Two polygonal closed sipes 20 spaced apart in the circumferential direction of the tire are attached to each block 19 of the block row located at the center in the width direction of the tire.
21 are formed, and small blocks 22, 23 and 24 are formed on the inside and outside thereof, respectively.

Therefore, in this example, each block 25 of the block rows adjacent to the central block row is not divided into small blocks.

According to each of the embodiments described above, by making the sipes formed on the blocks closed sipes, the kicking side portion of each small block partitioned by the sipes can be used in the rotational direction of the tire. can sufficiently reduce the amount of deformation in the opposite direction, and also reduce the amount of deformation of small blocks.
Since appropriate rigidity and sufficiently high tear strength can be provided, uneven wear and chipping can be effectively prevented while maintaining sufficiently high wet resistance and wear resistance of the tire.

Note that the same effect can be brought about here also when closed sipes are formed in the same manner as described above in a tire having a tread pattern including ribs and/or lugs in addition to blocks.

[Comparative example]

A comparative test of wet resistance, abrasion resistance, uneven wear resistance, and chipping resistance between the tire of the present invention and a conventional tire will be explained below.

Sample Tire: The tires of T B R11R24,5 were different only in the tread pattern, as described below, and the other basic tire structures were the same.

Conventional product A: Two types of tires with tread patterns without sipes as shown in Figure 4 (a) and (b). Two types of invented tires having tread patterns shown in FIGS. 5(a) and 5(b): The tread pattern shown in FIG. 1.3, in which the sipes of the present invention are applied to each tread pattern of conventional product A. Here, for both the conventional product B and the invention product, the sipe width was 0. mm and the sipe depth was 13n+m (leading depth was 16.5 mm).

Test conditions: Wet resistance: Under normal internal pressure and normal load, the tire was mounted on the drive shaft of the flat body trunk, and the speed was 59 km/h on a test course with a unit road surface of about 1 water layer.
It was evaluated based on the braking distance when pre-king.

Wear resistance, uneven wear resistance, and chipping resistance: Tires with normal internal pressure and load on standard U.S. highways.
An actual vehicle test was carried out by attaching it to the drive shaft of a truck tar head that moves with a trailer.

Wear resistance was evaluated by the mileage until the end of the tread life, and uneven wear resistance was evaluated by the amount of heel-and-toe wear difference that occurs on the front and rear ridges of the sipe after 100,000 miles of running. The chipping resistance was evaluated based on the number of chips that tend to occur due to siping after the tire had been driven for 100,000 miles.

Evaluation: The overall evaluation of the two types of conventional tires B was expressed as an index of 100, and the larger the index, the better the results. Here, both the indexes of conventional A and the invention product indicate the overall evaluation of the two types of tires.

The results of such comparative tests are shown in Table 1. According to the tire according to the invention, wet resistance and wear resistance can be maintained sufficiently high, and uneven wear resistance and chipping resistance can be effectively improved. That is clear.

(Effects of the Invention) Therefore, according to the present invention, by making the sipes formed in the block closed sipes, the mutually contradictory requirements of wet resistance and abrasion resistance and uneven abrasion resistance and chipping resistance can be achieved. It is possible to provide a heavy-duty pneumatic tire that satisfactorily satisfies the above requirements.

[Brief explanation of the drawing]

Fig. 1 is a diagram illustrating the tread pattern of the present invention, Fig. 2 is a graph showing the influence of closed size on uneven wear amount and wet resistance, and Fig. 3 is a tread showing another embodiment of the present invention. Pattern diagrams and Figures 4.5 are diagrams showing the tread patterns of conventional tires, respectively.

Claims (1)

[Claims] 1. A pneumatic tire for heavy loads having a tread pattern including blocks, wherein the blocks are provided with closed sipes.